Does your '88 Ford 460 have a Holley carb?
I had an 87 F350 dump truck with the 460, and it had a Holley 4bbl carb. At one point, the performance really started lagging, and no one could figure it out. After a bunch of internet searching I found out that the Holley carb has a rubber "power boot" that hardens over time and causes engine lagging / issues.
A friend did a "rebuild" of my carb which included replacing the rubber "power boot", and low and behold the engine ran almost like new.
I also found with the carb engine that I had to find a mechanic who knew how to work on one - they are aging out of the workforce.
Something to check!
P.S. I'm not sure if I am using the right terminology or where the power boot is, but that is what I read and how it was explained to me.